The present invention uncovers a system to superpose the modulated “ON”-lights of stereo-isomeric micro electro mechanical systems (MEMS). The invention relates to display and projection systems using MEMS as image modulators. More specifically, the invention relates to the chirality (handedness) of deflectable micro mirror devices (DMD) and uncovers solutions for some of the geometric problems associated with this handedness.
These geometric problems result from the physical layout of DMDs, which have their single deflectable mirrors rotated on a mirror deflection axis (MDA), which is the diagonal of single deflectable mirrors, for various physical reasons (U.S. Pat. No. 5,600,383). As a consequence, the MDAs are rotated 45 degrees with respect to the modulators mirror array (FIG. 1). While this usually has no consequence for the modulated “ON”-beam (because it is reflected normal to the chip surface in the most common use according to the state of the art), it introduces spatial consequences for the guidance of the unmodulated “IN”-beam. The overall system is thus a stereo-isomer. In systems with several superposed MEMSs (U.S. Pat. No. 5,638,142, U.S. Pat. No. 6,250,763) this problem is overcome by using a second reflective surface in addition to the single surface which is used for splitting the “IN”-beam and combining the modulated “ON”-beam.
In contrast, in our related application and in this application we focus on solutions which allow the system designers to superpose the MEMSs without the use of a second reflexion.